An issue existed in the handling of encrypted Mail. This issue was addressed with improved isolation of MIME in Mail. This issue is fixed in macOS Mojave 10.14.4, Security Update 2019-002 High Sierra, Security Update 2019-002 Sierra. An attacker in a privileged network position may be able to intercept the contents of S/MIME-encrypted e-mail.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-8645
Reference (s):
- https://support.apple.com/en-us/HT209600
- URL: https://support.apple.com/en-us/HT209600